Centrifugally cast plunger and tube



y 9 1940 w. F. HIRSCH ETAL 2 207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1938 3 Sheets-Sheet 12 8 /0 A gk I Wfim INVENTORS WALTER E HIRSCH FRANK B. BAYLEss y 9, 1940-w. F. HHRSCH ET AL 2,207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1933 5 Sheets-Sheet 2M \jx/x x 7 INVENTORS WALTER E H/RSCH FRANK 5. B YLEss t g iATTORNEY.

y 9, 1940- w. F. HIRSCH ET AL 2,207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1938 3 Sheets-Sheet 5m YA INVENTORS WALTER F Hl/ZSH FRANK B. BAYLESS Patented July 9, 1940UNITED STATES CENTRIFUGALLY CAST PLUNGER AND TUBE Walter F. Hirsch,Huntington Park, Calif., and Frank B. Bayless, Oil City,'Pa., assignorsto Industrial Research Laboratories, Ltd., San

Francisco, Calif., a corporation of Nevada Application February 14,1938, Serial No. 190,454

16 Claims.

This invention relates to cylindrical plungers as particularly used foroil well and other pumps, and to tubular and cylindrical objectsgenerally, and the invention has for its principal purpose theproduction of such objects of wear-resisting alloys or metals bycentrifugal casting, and particularly the production of such objectswith the main or body portion formed wholly of such wear-resistingmetal. A specific object of the invention is the production of dense,accurate centrifugally cast objects of the character mentioned fromextremely hard substantially unmachinable alloys which can only bepractically finished by grinding, and the maintaining of said grindingrequirement at the very minimum.

Other objects and advantages of the invention will appear in thefollowing description and accompanying drawings.

In the drawings: 1

Figure 1 is a longitudinal sectional view of a tubular casting assemblycomplete with its charge of alloy, for the centrifugal casting of aplain pump plunger section, or hard metal tube in accordance with ourinvention.

Figure 2 is a view similar to that of Figure 1, but showing the alloyafter melting and spinning in place within the outer shell.

Figure 3 is a longitudinal sectional view of the finished hard metaltubular section after ma chining off the outer shell and end closuresand grinding the surface.

Figure 4 is a longitudinal sectional view showing several of the hardmetal sections of Figure 3 assembled on an inner supporting tube to forma pump plunger.

Figure 5 is a longitudinal sectional view of an assembly similar to thatof Figure 1, but providing end hubs or connecting ferrules for thecylinder to be cast.

Figure 6 shows the assembly of Figure 5 after centrifugal casting.

Figure '7 shows the finished and threaded product from Figure 6.

Figure 8 is a longitudinal sectional view of an r assembly similar tothat of Figure 5 showing a modified form of the end hubs or ferrules.

Figure 9 shows the assembly of Figure 8 after centrifugal casting.

Figure 10 shows the finished product from Figure 9.

Figure 11 is a longitudinal sectional view similar to that of Figure 9,but showing a central hub or ferrule in the assemblage.

Figure 12 is a longitudinal sectional view of an assembly similar tothat of Figure 5, but showing a modified form of tapered end hubs orferrules.

Figure 13 shows the finished product made from the assembly of Figure12.

Before describing the invention and drawings in detail it may be statedthat heretofore it has been known to line a steel or iron tube orcylinder with hard or wear-resisting metals or metal alloys melting atmore than 1000 F., by centrifugally forcing the molten layer against thewall of the tube or cylinder by rapidly spinning the same until themetal chilled to a dense smooth internal layer firmly bonded to thetube. Brown patents, No. 1,923,075 and No. 2,033,814, and also Kormannet al. Patent No. 2,046,914 clearly illustrate the prior art of theinternal centrifugal lining of tubes and other circular hollow articleswith various metals and alloys, such as hearing metals, bronze,stellite, hard boron-iron alloy, etc., and more recently a variation ofsuch processes of centrifugal casting has come into usage for thecentrifugal lining or casting of a thin layer of wear-resisting hardalloy on the exterior of shafts and tubes for use as pump plungers andpistons in the handling of gritty liquids, such as oil and other pumpservice, etc.

Such centrifugally exteriorly hard lined shafts and tubes have onlyfound limited use in industry, and it is one of the objects of thepresent invention to overcome the difficulties and uncertaintiesattendant upon the production of such exteriorly hard-lined plungers, asit produces a better wear-proof plunger of dense centrifugally cast hardalloy, yet avoids entirely the former necessity of forcing the moltenalloy into a very narrow space formed in the casting assembly betweenthe outer surface of the shaft or tube to be covered and the innersurface of an outer surrounding shell or temporary mold which later wasmachined away from the thin hard layer.

In the exterior coating or lining of tubes and shafts with extremelyhard alloys, particularly of the stellite or boronized iron type, whichare substantially unmachinably hard, so that they can only be exteriorlyfinished by grinding, it is manifest that the layer as cast should be soaccurate as to require only the minimum of grinding to reduce it to theactual finished dimension desired, otherwise the cost would make the useof the article prohibitive in industry; also that if a steel tube wereto be lined exteriorly without increasing its diameter objectionably,the coating applied would have to be very thin, and hence the castingspace between the exterior of the tube or shaft to be coated and theouter or casting shell would be but a mere annular crack into which themolten metal would have to be forced, and with a result that the layersare sometimes imperfect, lacking in density, continuity, or contain gasbubbles, as such annular casting spaces or cracks are not easily ventedto permit escape of gas.

The present invention in overcoming the difficulties pointed outprovides a centrifugally cast tube or hollow plunger of exterlorlyunmachinably hard or other wear-resisting metal or alloy bycentrifugally forming the tube or plunger entirely of the metal or alloyand hence dispenses with the centrifugal forcing of such high meltingpoint metals into narrow annular spaces as formerly required in order toform dense hard exterior facings, and makes it much simpler and quickerto produce the required articles, while insuring perfect results at alltimes.

Briefly described, the invention in its simplest form comprisesproviding a cylindrical outer, preformed metal tube or temporary castingshell of readily machinable metal such as of steel or iron, and of aweight or thickness just suflicient to insure rigidity during thecasting and spinning operations, and applying an inner, very thick layerof r the desired wear-resisting alloy or metal within the tube byspinning the tube, while hot, horizontally on its axis to force thealloy in molten state in the tube against the inner wall of the tube toform the desired concentric layer thereon, and continuing the spinninguntil the layer has set, then removing the outer shell from the layer asby destructively machining or stripping it therefrom, and thereafterfinishing the surface of the hard layer by grinding, as the alloy isgenerally firmly bonded to the temporary outer shell by the castingoperation. The actual thickness of the layer applied by centrifugalcasting is suflicient to produce (when the outer shell has been strippedfrom it) a rigid self-sustaining tube of solid hard alloy which isusable as such for the purpose of a pump plunger or working piston, thusdispensing with the heretofore required further bonding of the layereither externally (or internally) to another tube for permanent support.

Another important advantage of forming such articles of the solid hardmetal instead of by applying thin layers to either inner or outer steelsupporting tubes, is that in the latter method there is a dilution ofthe alloy and its properties become impaired through its molten contactwith the. supporting tube, tubes, or shaft, on account of the relativelythin layer of lining or facing metal used as against the heavy mass ofthe supporting body, and which is substantially eliminated by theimproved method.

The hard, centrifugally formed tube thus produced may be groundexternally, or internally, or both, depending on the use intended. As afinal form of the invention the centrifugally cast tube may have endhubs or ferrules cast in place or inserted afterward and secured as bysoldering or welding, to serve as connections, aligning of severalsections, threading, etc.

In the variations shown in the drawings the outer or temporary shell,preferably a preformed wrought steel tube, is for uniformity designatedI in all of the figures, and the centrifugally cast layer ofwear-resisting or hard metal alloy is designated 2, and the finishedarticle from each respective assembly is designated 2 2 2 2 Thearrangement shown in Figure 1 is a casting assembly for the productionof the article shown in Figure 3, and the assembly comprises a preformedwrought steel or iron outer tube or shell I, closed at both ends bytightly fitting flanges 3 preferably welded in place clear around as at4 to prevent possible leakage of molten metal while spinning, or theflanges may otherwise be tightly sealed in place as by threading orbeading over, if desired, and at least one of the flanges is providedwith a very small central vent hole 5 to permit escape of air or gasesformed during the heating of the assembly, to

melt the alloy or hard metal 6 which is preferably as it melts at about2000 F. The charging metal may of course include a fluxing agent to makeIt flow better, if desired,

The assembly is best heated by slowly revolving it in a suitable furnaceuntil the alloy inside has completely melted, and it is then removedfrom the heat zone and spun horizontally on its axis in any suitablemachine, at a high rate of speed suflicient to throw the molten metalagainst the inner wall of tube I in an even layer and kept spinning tillthe layer has chilled, as indicated at 2 in Figure 2. when furthercooled, the outershell I, which generally becomes firmly bonded to thecasting, is destructively removed from the inner cast hard metal tube 2,as by machining it off in a lathe or otherwise, and after which theouter and/or inner surface of the hard metal tube is ground to perfectcylindrical form as may be desired for use. The end flanges aresimilarly cut away either before or after the exterior grindingoperation, as may best facilitate the operation, and the ends of thehard cylinder may be squared oil! or ground slightly convex and concaveas indicated respectively at G and I in Figure 3 so as to provide meansfor more readily centering a series of such tubes or 7 sections 2' on amandrel 8 in Figure 4.

In Figure 4 the mandrel is shown itself as a hollow tube threaded atboth ends and provided with clamping nuts 9 and III each having one endeither concave or convex to center with the adjacent end of the hardmetal section as indicated. For some purposes the supporting mandrel maybe solid, and in other cases the mandrel may be entirely dispensed withas will hereinafter appear.

Insofar as the present invention is concerned the hard metal alloy,instead of being melted within the closed outer shell, may be pouredinto it during the spinning operation through an enlarged centralopening taking the place of vent 5 or provided at the opposite end, itbeing understood that the shell be first preheated to prevent prematurechilling of the melted casting metal. Any desired metal melting at asubstantially lower temperature than the outer shell may be used whenmelting the metal within the shell, but when pre-melting and pouring itin while spinning, a metal melting at even a higher temperature than theshell may be used, as it will cool before material injury to the shell,especially it outside air circulation be used.

The metal when introduced in the solid state may be in broken pieces, orin bar form, in fact it may substantially fill the interior of the shellwhere a very thick tube of the alloy is required as a final product.

If the assembly is held vertically while spinning and sumcient alloy isplaced inside or introduced while spinning it is manifest that solidbars or shafts of the hard alloy may be centrifugally produced insteadof the more useful tubular form of product. A bar thus centrifugallyproduced will have an extremely dense outer surface free fromimperfections usually resulting from other methods of casting.

In view of the complete description set out in connection with Figures 1to 4, only the points of variation therefrom will be taken up in regardto the remaining figures as the handling is the same for all forms.

Figure 7 shows the solid hard alloy tube 2 provided with soft or machinesteel ends or ferrules ll threaded exteriorly as at l2, or internally ifdesired, to provide for connection to other members. These machinableends are produced by providing special machine steel end closures forthe shell I as indicated at l3 in Figure 5, and which closures arepreferably hollow or pre-bored for most of theirlengthas at It toovercome the necessity of doing this later on, and they are reduced indiameter at their inner ends as at l5,

and also preferably tapered so as to become encased in the hard metalalloy tube 2 when cast as shown in Figure 6, and after which the outertube or shell I is removed as described for Figure 2 and the inner endsl6 of the closures bored through and the tube ground exteriorly, and/orinteriorly. It is manifest that if less alloy is used, or if bore I4 isnot finally enlarged to the full diameter of the hard metal tube, thatthe end ferrules will project inward within the tube 2 as dotted at H inFigure 7, and which is advantageous for some purposes. With a castingassembly as shown in Figure 5, one or more additional small vent holesare required as at 5 where the hard metal overlaps the ferrule ends.

Figure 10 shows the solid alloy tube 2 provided with inwardly projectingferrules i1 formed from annular members l1 projecting inwardly from theclosure fianges 3' of the casting assembly of Figure 8. Figure 9 showsthe assembly after spinning and with an inner shoulder ll" formed atboth ends of a size depending on the amount of alloy used, but whichshoulder generally need be only suflicient to provide for boring theferrules without striking the hard tube 2 with the tool. Thisfacilitates aligning a plurality of the finished tubes on an innermandrel in the general man ner shown in Figure 4, or provides forinternal threading of the ends.

The casting assembly of Figure 11 is similar to that of Figure 8, butshows the provision of two outer shells l abutted endwise and welded atl8 and a central ferrule or hub IS. The final product of this assemblyafter the end closures 3" were cut off would be like that shown inFigure 10 with an additional centrally located ferrule. or it wouldproduce two articles as shown in Figure 10 if transversely cut throughthe weld 18.

Figure 13 shows a hollow hard alloy pump plunger 2 with inwardlyprojecting tapered end ferrules l9 completely embedded in the hard alloyand with outer ends counterbored and internally threaded as at 20 forattaching to pump fittings, valve cages, etc.

The assembly for producing this is shown in Figure 12, and is similar tothat of Figure 5, except that the end closure plugs 2| are initiallybored part way from their inner ends as indicated at 22 instead of fromthe outer ends as indicated at H in Figure 5.

The final product shown in Figure 13 comprises a relatively thicktubular plunger 2 of solid hard alloy or wear-resisting metal such asthe boron-nickel-iron alloy mentioned, or of the stellite type, hardwhite iron, or any other type or variation of these metals desired, andprovided with machine steel connecting ferrules welded or bonded intothe plunger at one or both ends either of slightly smaller diameter thanthe hard working surface of the plunger as indicated in Figure 13, or ofthe same diameter. The ferrule may have a rough cut on its outer surfaceas indicated, to facilitate bonding to the molten hard metal layer whenspun, and the tapering of the inner ends of the ferrules avoids any lineof weakness in the plunger which might cause a transverse fracture inthe hard tube.

In considering the present invention and prod not of a hollow or solidpump plunger or piston of solid, unmachinably hard alloy, as against theexteriorly hard-faced wrought steel tubular or solid plungers of thekind heretofore made, as explained on page one, its chief points ofadvantages are that being of solid alloy instead of a facing, it is freefrom any cracking or chipping tendencies, also free from entrapped airor other gases, or scale particles so liable to be developed in thenarrow annular crack in which the facing type of hard coating had to beforced, and since the spinning operation is conducted in a plain hollowtube or shell it may be much more easily and quickly produced, and thecentrifugal castings are always of dependable density and soundness.Besides this, the casting assembly is simpler and cheaper than requiredfor the exteriorly faced article. of production of this improved productis such that is has practically supplanted the exteriorly faced articlein oil well and other pump plungers for which the invention wasprincipally developed.

We have tried producing such plungers wholly of hard alloys by thecommon sand and permanent mold method of casting, but found that thedifficulty of obtaining defect-free outer surfaces, and also theexcessive amount of grinding required to bring the articles to therequired condition was prohibitive. Besides this the centrifugal castingmethod of the invention not only insures freedom from surface defectsand reduces the finish grinding to the very minimum, but also producesan increasing density to the metal which reaches its maximum at theouter or working surface of the article, and adds considerably to thestrength of the casting.

While it is one of the objects of the invention to provide a method ofmaking such plungers of extremely hard alloys which could not beotherwise produced, the word alloy as used in the claims, is intended tocover any desirable metal useful for the purpose intended whetherstrictly considered as an alloy or not.

Having thus described our invention, what we claim is:

1. The method of producing hard alloy cylindrical objects whichcomprises providing a preformed cylindrical shell of readily machinablemetal of an internal diameter slightly larger than the finished diameterof the desired object, spinning the shell and a mass of the molten alloywithin the shell under conditions to produce a dense concentric mass ofthe alloy in said shell and until the mass solidifies, and thereafterdestructively stripping or machining the shell from the solid objectproduced and finishing the surface of the object.

2. The method of producing hard alloy metal tubes or rods whichcomprises providing a preformed shell of readily machinable metal of aninternal diameter slightly larger than the finished diameter of thedesired metal tube or rod, substantially sealing the ends of the shell,and spin- In fact the superiority and ease P ning the shell on its axistogether with an internal charge of molten metal alloy sufficient toyield a tube of the thickness desired under the action of.centrifugalforce and until the tube or rod has chilled, and thereafterdestructively stripping or machining the shell from the centrifugallycast tube or rod and finishing the surface of the latter.

3. The method of producing hard alloy tubes which comprises providing apreformed tubular shell of readily machinable steel, placing a charge ofthe desired alloy within the shell, providing end closures for the shellhaving annular portions extending inwardly into the shell in spacedrelation to its inner surface and one of said closures being vented,thereafter heating the assembly to melt the alloy, spinning the assemblyto distribute the molten alloy evenly within the shell and embracingsaid annular portions and maintaining the spinning until the alloy haschilled, and thereafter stripping or machining the shell from the alloytube thus formed and removing the end closures while leaving the annularportions attached to the tube, and finishing the surface of the tube.

4. The method of producing hard alloy tubes which comprises providing arelatively thin preformed tubular shell of readily machinable steel,placing a charge of the desired alloy within the shell, providing endclosures for the shell, an annular portion extending from one of saidclosures inwardly into the shell in spaced relation to its innersurface, and one of said closures being vented. thereafter heating theassembly to melt the alloy, spinning the assembly to distribute themolten alloy evenly within the shell and embracing said annular portionand maintaining the spinning until the alloy has chilled, and thereafterstripping or machining the shell from the alloy tube thus formed andremoving the end closures, and finishing the surface of the tube.

5. A centrifugal casting assembly comprising a preformed steel tube,closures at both ends of the tube, and at least one of said closuresprovided with a cylindrical extension projecting a relatively short wayinto the tube in spaced relation to its inner surface, and a charge ofmetal alloy within the tube adapted to be melted therein withoutsubstantial injury to the tube.

6. A centrifugal casting assembly comprising a preformed steel tube,closures at both ends of the tube, and at least one of said closuresprovided with a cylindrical extension projecting a relatively short wayinto the tube in spaced relation to its inner surface, and a charge ofmetal alloy within the tube adapted to be melted therein withoutsubstantial injury to the tube, said extension ta'pering to smallerdiameter toward its inner end.

7. A pump plunger or the like comprising a relatively thick uniformcylindrical tube of solid dense cast hard metal alloy having thecharacteristics of centrifugally cast metal, and provided with means atits ends for aligning in abutting relation with similar tubes.

8. A pump plunger or the like comprising a relatively thick cylindricaltube of solid dense cast substantially unmachinably hard metal alloyhaving the characteristics of centrifugally cast metal, and providedwith an integrally attached machinable steel'ferruie at the end.

9. A pump plunger or the like comprising a relatively thick cylindricaltube of solid dense cast substantially unmachinably hardboron-nickeliron alloy having the characteristics of centrifugally castmetal, and a ground exterior surface.

10. A pump plunger or the like mprising a relatively thick cylindricaltube of solid dense cast substantially unmachinably hard metal alloyhaving the characteristics of centrifugally cast metal, and providedwith machinable steel ferrules at its ends embedded and bonded into themetal of the tube.

11. A pump plunger or the like comprising a relatively thick cylindricaltube of solid dense cast substantially unmachinably hard metal alloyhaving the characteristics of centrifugally cast metal, and providedwith machinable steel ferrules at its ends embedded and bonded into themetal of the tube, said ferrules being of tapered reduced thickness asthey extend into the metal of the tube and being embraced both insideand outside by the tube metal.

12. A pump plunger or the like comprising a relatively thick cylindricaltube of solid dense cast substantially unmachinably hard metal alloyhaving the characteristics of centrifugally cast metal, and providedwith ferrules of machinable steel at its ends bonded thereto, and asimilar ferrule intermediate its length bonded thereto.

13. In a method as set out in claim 4, the additional step of securing aferrule in said shell intermediate said closures, and with the ends ofthe ferrule spaced inwardly from the inner surface of said shell.

14. A pump plunger or the like comprising a plurality of relativelythick cylindrical tubes of solid dense cast hard metal alloy having thecharacteristics of centrifugally cast metal, assembled in abutting endto end alignment, and provided with means holding them together.

15. The method of producing cylindrical metal objects which comprisesproviding a preformed cylindrical shell of readily machinable metal,spinning the shell about its longitudinal axis with a mass of the moltenmetal desired within the shell under conditions to produce a denseconcentric mass of the metal in said shell and until the masssolidifies, and thereafter destructively stripping or machining theshell from the metal object thus produced, the thickness of said metalobject being sufllcient to make it self-sustaining for furthermechanical operations.

16. The method of producing metal tubes which comprises providing apreformed tubular shell of readily machinable metal, substantiallysealing the ends of the shell, and spinning the shell about itslongitudinal axis together with an internal charge of the molten metaldesired sufficient in quantity to yield a tube of the desired thicknessunder the action of centrifugal force and until the tube has chilled,and thereafter destructively stripping or machining the shell from thethus centrifugally cast tube, the thickness of the wall of said tubebeing suflicient to make it self-sustaining for further mechanicaloperations.

WALTER F. HIRSCH. FRANK B. BAYLESS.

